1. Field Of The Invention
The present invention relates to a display apparatus, and more specifically to a data transfer system for transferring data to a data drive circuit of a dynamic drive type display apparatus.
2. Description Of Related Art
A typical conventional display apparatus includes a signal control circuit receiving a vertical synchronizing signal and a horizontal synchronizing signal and generating a scan control signal, a driver signal and a latch signal. In response to the scan control signal, a scan drive circuit sequentially drives a number of scan electrodes of a display panel. On the other hand, a data drive circuit receives a data signal and a clock signal and is controlled by the driver signal and the latch signal so as to drive a number of data electrodes of the display panel. The data drive circuit is composed of for example a driver, a latch and a shift register. The clock signal is a dot clock in synchronism with the data signal.
With the above arrangement, the display panel is driven in a line sequential scanning manner from a first line to a final line in accordance with the horizontal synchronizing signal, and this scanning is repeated 7ith reference to the vertical synchronizing signal. For this purpose, during one period of the horizontal synchronizing signal, a number of items of data corresponding to display cells of one scan line are serially supplied to the shift register of the data drive circuit in synchronism with the clock signal, and after the data has been written to the shift register, a content of the shift register is transferred from a parallel output of the shift register to the latch. The display cells on one scan line selected by the scan drive circuit is energized or deenergized by the driver of the data drive circuit on the basis of the data held in the latch during one period of the horizontal synchronizing signal, namely, in one scanning period.
The above mentioned conventional display apparatus is such that the data signals are serially transferred to the shift register. Therefore, since a required frequency of the clock signal and the data signal increases in proportion with increase of a display capacity, the shift register having a high operating frequency has been required.